Wax Melt Molds & Clamshell Compatibility: Cavity Weight Targets

Your wax melt weighs 2.8 oz but the clamshell pocket fits 2.5 oz - the lid bows, FBA rejects the shipment, and you re-pour 600 cavities. RUUIPON builds custom wax melt molds at MOQ 50 with prototypes in 3-7 days. This guide ties cavity weight to clamshell compatibility so fill weight, snap closure, and mold geometry align before production pour.

Quick answer: Match cavity fill to clamshell spec: common retail targets 2.5 oz (71 g), 2.8 oz (79 g), or 3.2 oz (91 g) per melt. Mold cavity volume +3-5% above target weight for shrink and meniscus. Snap clamshells need flat melt base ±0.5 mm and max OD 0.5 mm under pocket ID. Shore A 28-35, walls 2.5-5 mm, spacing 8-20 mm.

Weight Targets vs Clamshell Pockets

Retail label	Target fill weight	Cavity volume @ 0.90 g/ml wax	Clamshell note
2.5 oz bar	71 g ±2 g	~79 ml	Standard 5-cell pack
2.8 oz bar	79 g ±2 g	~88 ml	Premium single cavity
3.2 oz bar	91 g ±2 g	~101 ml	Wide snap lid
1 oz mini	28 g ±1 g	~31 ml	Sampler 6-pack

Clamshell Packaging Standards

Buy clamshells first - mold to pocket, not reverse. Common suppliers publish pocket ID, depth, and max stack height.

• Pocket ID - melt OD must be 0.5-1.0 mm smaller per side for drop-in without bowing lid.
• Pocket depth - melt height +0.5 mm clearance minimum; +2 mm if embedments.
• Flat base - clamshell sits on shelf; domed base rocks - spec flat within 0.5 mm.
• Stack height - FBA carton limits; five melts × height must fit case pack.

General wax guide: wax melt mold guide. Candle overlap: candle manufacturing.

Cavity Weight Targets & Volume Math

Wax density ~0.85-0.95 g/ml depending on fragrance load and soy vs paraffin blend. Design cavity volume at high end of density range.

Wax type	Density used for calc	71 g target volume	79 g target volume
Soy 8% fragrance	0.88 g/ml	81 ml cavity	90 ml cavity
Paraffin 6% fragrance	0.90 g/ml	79 ml cavity	88 ml cavity
Beeswax blend	0.92 g/ml	77 ml cavity	86 ml cavity

Prototype weigh 10 pours on sample tray - average must hit ±2 g before MOQ 50 approval. Gummy volume method similar: cavity volume guide.

Cavity Geometry & Demold

Feature	Spec	Clamshell fit impact
Top OD	Clamshell ID −1 mm total	Too tight = lid stress
Base OD	≤ top OD (2° draft)	Drop-in alignment
Corner radius	≥2 mm	Prevents wax corner snap
Emboss logo	0.3-0.5 mm depth	Does not change OD fit
Undercut	None on side walls	Stick + scuff clamshell

Undercut limits: undercuts & draft. Tear on demold: tear strength.

Fragrance Load & Release

High fragrance softens wax surface - sticks in deep texture. Shore A 28-32 silicone compensates; stiff Shore A 40 tears on demold at 45 °C pour temp.

• Pour temp - 60-75 °C typical; do not exceed silicone rating.
• Cool demold - 18-22 °C room; freezer demold risks condensation on clamshell pack day.
• Surface finish - gloss cavity = shiny melt face for retail. Surface finish.

Cycle tracking: cycle life by application.

Multi-Cavity Tray Layout

Layout	Cavities	Spacing	Hourly output (manual)
Bar sheet	6	12-18 mm	~40-60 melts/hr cooled
Bar sheet	12	10-15 mm	~80-100 melts/hr
Single shape	4 large	15-20 mm	~25 melts/hr

Layout: multi-cavity layout. Walls 2.5-5 mm; vacuum-degassed pour ~0.1% shrink.

Production Spec at MOQ 50

PO line	Example
Target weight	2.8 oz (79 g) ±2 g
Clamshell SKU	Buyer supplies pocket ID drawing
Melt OD	Pocket ID −1.0 mm
Silicone	Shore A 30, platinum cure, vacuum degassed
Sample	10-weight log + clamshell fit photo in 3-7 days

Send clamshell spec + wax formula density to [email protected] | Contact RUUIPON | WhatsApp +86 135 3006 2969.

Frequently Asked Questions

Mold first or clamshell first?
Clamshell first - always.

Can one mold fit two clamshell brands?
Only if pocket ID matches within 0.5 mm - verify before quote.

Domed top melt for branding?
OK if total height ≤ pocket depth −1 mm.

Snap vs slide clamshell?
Snap needs tighter OD control - spec −1.0 mm not −0.5 mm.

MOQ?
MOQ 50 trays per design.

Amazon FBA weight claim?
Mold cavity targets label weight - Amazon FBA guide.

Color swirl cavities?
Same volume spec - swirl does not change weight target.